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Lecture

Nov. 30 - 2B03.docx

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Department
Astronomy
Course Code
ASTRON 2B03
Professor
Laura Parker

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Nov. 30 – 2B03 30/11/2011 10:26:00 AM Friday – content not on the final exam. What makes a particle “elementary”?  This goes back all the way to the Greeks. If a particle is truly elementary, it cant be subdivided. o No inner structure.  Standard model – fundamental particles are quarks and leptons.  Quarks - 6 flavours, only up and down are important though (protons and neutrons). st o And Leptons – electrons and electron neutrinos – 1 colomn only one important. o With very energetic events, you can create the other ones – normal life just 1 column though. Baryonic – everything made up of protons and neutrons – NORMAL STUFF WIMP dark matter would be “non-baryonic”  Not made up of protons and neutrons. Baryons – 3 quarks. Mesons – 2 quarks.  Only difference. 4 Forces  4 force carriers – have to do w/ 4 forces.  Describing the 4 forces w/ force carriers. o 60s, 70s – Feynman describing force in a new way. o Photons are the force carriers of electromagnetic force. o Weak force - has a couple different force carriers. Things which have only been detected in high energy particle accelerators. o Strong force - force carrier is gluons (like elastic bands) o Gravity – graviton (unobserved) Grand unified theories of physics – combine 3 forces. Some possible, but no theory has been tested and is confirmed.  As we go earlier and earlier in the universe (1 second old) – forces merged together. Today we have 4 forces; as we go back – we can see when they unified (electroweak @ 12 seconds after).  THe more you go back, forces were 1.  A "theory of everything" would explain all 4 forces. Matter vs. Anti matter  For every particle in the standard model, there is an anti particle. o An opposite electric charge. o eg. Up vs anti-up. We can make anti-matter  Cosmic ray shower – high energy particle in space. o can come from supernovae explosions, suns.  Proton from sun slamming into atmosphere (llike a makeshift particle accelerator) – a bunch of reactions. Other particles form.  When an electron and positron hit each
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